The present invention relates to a code data reading apparatus for photographic film which is capable of reading a bar code data from a photographic film with a camera or print station.
In a photographic printing process, a film is advanced by a film feeder until its frame to be printed comes to an exposure means and is projected for printing the frame on a sheet of photosensitive paper which is then subjected to a developing process. For printing a desired picture, its relevant data, e.g. ID(DX) code and frame number, recorded in a bar-code format on the negative film is detected and read with an optical sensor to identify the frame and obtain the conditions for the developing process. To do so, the film feeder is provided with a light emitter, e.g. LED, and a bar code detector for reading the bar code of the desired frame from the film.
One such code data reading apparatus for photographic film is disclosed in Japanese Patent Laid-open Publication 4-350646 (1992) which employs a CCD line sensor as the bar code detector. The CCD line sensor scans a target frame of a negative film to read specific sets of pixels at four points and, simultaneously, identify a bar code from a row of pixels extending widthwise of a negative film.
Another code data reading apparatus for photographic film is described in Japanese Patent Laid-open Publication 4-310938 (1992) where an optical image of a bar code is produced by a light emitter, focused by a lens, and received by a bar code detector (or sensor). In particular, a slit plate having a slit opening arranged therein to be smaller in a width than the smallest stripe of the bar code is disposed between the lens and the bar code detector. As the bar code detector receives an intensity of light passed through the slit, it can read the bar code which has been recorded at high density.
Also, a further code data reading apparatus is disclosed in Japanese Patent Laid-open Publication 5-19367 (1993) which employs a specific code detecting method for increasing the accuracy of reading of a bar code data from a negative film with no use of any high-precision optical sensor. According to the code detecting method, the base (blank) and the code (stripe) of a bar code are detected and converted to their respective minimum and maximum signals of peak values with a common optical sensor. The peak values are then compared with predetermined thresholds to examine whether or not they represent the base and code of the bar code.
It is important for correctly reading the bar code with the bar code reading apparatus to ensure that the negative film is not undulated and is prevented from stagger movements during the transfer. Commonly, the width of the transfer passage for the negative film is minimized to prevent the stagger movements or the bar code detector is mounted to a frame member which is movable to trace the stagger movements of the film, thus allowing the bar code detector to read the bar code of the negative film as being located at a distance inwardly from one edge of the film.
Although the above prior art read apparatuses are designed to read the bar code data correctly from the negative film, no one but the first mentioned read apparatus can have a scheme for correctly reading the bar code data from the negative film which is undulated at its surface or travels with stagger movements.
The first prior art apparatus permits the line sensor to detect the widthwise end (or side edge) of a negative film and specify the pixels representing a bar code with reference to the widthwise end so that it reads the bar code data from the negative film which travels with stagger movements. It however fails to eliminate the problem that, as travel path of the negative film is not straight, undesired margins of light are passed between the film and its guide and/or through the bar code blanks thus interfering with the main transmission of light across the bar code and causing the reading of the bar code data to be difficult.
If the transfer passage for the negative film is narrowed for prevention of the film from traveling in stagger movements, the likelihood is increased of jamming the film in the passage. During traveling in stagger movements, the negative film allows the direct radiation of light from the light emitter to pass off its widthwise edge to the detector. As a difference in the intensity on the detecting surface of a sensor between the bar and blank transmitted lights through a bar code is decreased, a bar stripe signal produced by the detector is less distinguished from the signal representing the blank of the bar code. In other words, the transmission of light through the bar stripes of the bar code is hardly discriminated thus causing a reading error. In the case of undulation of the negative film, portions of the direct radiation of light from the light emitter may be passed through the perforations of a negative film to the detector, resulting in a reading error.
The foregoing problems will be explained in more detail referring to FIGS. 5 and 6. As shown, a sensor 21 is commonly disposed as close to a light emitter 23 as possible. The optical sensitivity of the sensor 21 is increased for enhancing the electrical accuracy. Also, the sensor 21 is adapted such that the detectable width Ws on its detecting surface is substantially equal to the width of the smallest bar stripe F' or blank F" of a bar code to minimize a power requirement for amplification of its output signal in an amplifier. Accordingly, even if the bar of the bar code on a negative film F is located just under the sensor 21 and exposed to the radiation of light from the light emitter 23 as shown in FIG. 5, a low intensity of light a2 passed through the bar stripe of the bar code is partially joined with high intensities of light b and c passed through the two blanks on both preceding and proceeding sides of the bar. As the result, the total intensity of light incident on the detecting surface 21a of the sensor 21 is not minimized and thus, a difference between the total intensity and the maximum intensity of light will become small.
It is ideal for transfer of the negative film that the film is driven with its two edges being guided by the passage of the film of which width L is not greater than that of the film. As shown in FIG. 6, two beams of light d1 and e1 emitted from the light emitter 23 are directed to the negative film F and then, transmitted portions d2 and e2 of the light beams after passing the film F fall on to the detecting surface 21a of the sensor 21. Accordingly, a difference in the intensity of light between the light transmitted through bar and the light transmitted through a blank of a bar code can be acknowledged. However, during the transfer, the negative film F is loaded with unwanted stress or strain and will thus cause jamming. In practice, the width L of the film passage is arranged to be larger than that of the film F, as shown in FIG. 6.
When case that the negative film F is undulated or staggered while traveling along the passage, portions f and g of the light directed from the light emitter 23 to the film F are permitted to pass through the perforations of or off the edge of the film F but not through the bar or blank of the bar code and run to the sensor 21 directly or indirectly as reflected on the walls of the film passage. This causes the intensity of light passed through the bar stripe to be amplified on the detecting surface of the sensor 21 with the unwanted light portions f and g propagated through the perforations of or off the edge of the film F. Accordingly, the total intensity of light received by the detecting surface of the sensor 21 is not minimized and thus, a difference in the intensity between the bar and blank transmitted lights becomes small. As the result, the intensity of light passed through the bar of the bar code will be less distinguished, thereby generating a reading error.
When the bar code detector is mounted to a movable member to trace the undulated surface of a negative film, its action depends on the smoothness of its mechanical movement. If the mechanism is fouled with dirt or dust, it causes a jerky action of the bar code detector impairing the reading of a bar code. Also, the movable member is disposed on an intermediate region of the film passage thus increasing the possibility of film jamming.
In any case, the detector which is set with its light detecting distance larger than the width of the smallest of the bar stripes or blanks of a bar code receives at one time two different intensities of light passed through both the bar and blank of the bar code and thus produces an electric signal which is closer to the signal representing the the blank. Accordingly, the difference in the intensity on the detecting surface of the sensor between the bar and blank transmitted lights becomes small. As the result, the intensity of light passed through the bar of the bar code will be less distinguished, thereby generating a reading error.
It is an object of the present invention to provide an improved code data reading apparatus in which, while a negative film is transferred along the passage of a feeder having such a width as not to cause jamming of the film, a bar code recorded on the negative film is projected by an enlarging means on the detecting surface of a sensor so that a difference in the intensity on the detecting surface of a sensor between the bar and blank transmitted lights through the bar code can be increased regardless of unwanted fractions of light passed off the edge of the film. Accordingly, reading error is eliminated and the bar code data can be read correctly.